As an alternative to animal testing, in vitro cell culture is a powerful technique in biomedical research to probe tissue functions, intercellular communications as well as cellular responses to environmental stimuli such as drugs and toxins. Recently, 3D in vitro culture (e.g., where cells are cultured in a porous scaffold and grown into a 3D tissue) has shown cellular physiology and functions that resemble in vivo cells and tissues, in contrast to conventional 2D culture (e.g., where cells are cultured on a petri dish and grown into a monolayer). See Pampaloni et al., Nature Review: Mol. Cell Biol., 8:839-845 (2007); Kawaguchi et al., BioMed. Research Int'l, 895967 (2013); Bahavand et al., Int'l Dev. Biol., 50:645-652 (2006). For example, maturation markers were more readily observed in 3D-cultured embryonic cardiomyocytes, and 3D scaffolds can often help retain contractile functions of the developing embryonic myocardium.
However, prevailing 3D scaffolds lack the ability to monitor cellular functions. Characterization of 3D-cultured cells still relies on digestion of the cultured cells followed by biochemical assays, histology assays, or other downstream assays, which are laborious and often lead to cell death.